Experimental Study of RCS Diversity with Novel No-divergent OAM Beams

TL;DR

The paper tackles limited RCS diversity under fixed illumination and energy-divergent traditional OAM beams by proposing energy-void-free NTCS-OAM beams generated with arc-shaped leaky-wave antennas at X-band. It provides both analytical modeling and full-wave simulations, and validates the concept with experiments on metal spheres, a model airplane, and a model ship, showing that different OAM modes produce distinct, mode-dependent RCS patterns. This demonstrates a new degree of freedom for radar target detection and characterization in intelligent transportation systems, with practical implications for long-range sensing and potential integration with dynamic beam-control technologies such as RIS and reconfigurable antennas.

Abstract

This research proposes a novel approach utilizing Orbital Angular Momentum (OAM) beams to enhance Radar Cross Section (RCS) diversity for target detection in future transportation systems. Unlike conventional OAM beams with hollow-shaped divergence patterns, the new proposed OAM beams provide uniform illumination across the target without a central energy void, but keep the inherent phase gradient of vortex property. We utilize waveguide slot antennas to generate four different modes of these novel OAM beams at X-band frequency. Furthermore, these different mode OAM beams are used to illuminate metal models, and the resulting RCS is compared with that obtained using plane waves. The findings reveal that the novel OAM beams produce significant azimuthal RCS diversity, providing a new approach for the detection of weak and small targets.This study not only reveals the RCS diversity phenomenon based on novel OAM beams of different modes but also addresses the issue of energy divergence that hinders traditional OAM beams in long-range detection applications.

Figures (8)

• Figure 1: A NTCS-OAM generator design without central energy void with respect to (a) the 3D radiation pattern from the front view, (b) the same radiation pattern from the left view (c) 2D beam schematic diagram showing the amplitude (solid line) and the phase (dashed line) distributions.
• Figure 2: Novel 2D radiation pattern of OAM mode with respect to (a) ${\ell _{\rm{e}}} = 23$, (b) ${\ell _{\rm{e}}} = 30$, (c) ${\ell _{\rm{e}}} = 35$, (d) ${\ell _{\rm{e}}} = 45$, comparing results between simulation (solid line) and measurement (dashed line).
• Figure 3: The EM wave illuminates a "simple" complex target consisting of two identical metal spheres, with respect to (a) by the conventional plane wave, and (b) by the novel OAM beam without central void.
• Figure 4: RCS results obtained when OAM beams with different mode numbers illuminate a "simple" complex target consisting of two identical metal spheres, which are compared to those obtained with plane waves. (a) Comparing with OAM mode $\ell = 1$. (b) Comparing with OAM mode $\ell = 2$. (c) Comparing with OAM mode $\ell = 3$. (d) Comparing with OAM mode $\ell = 5$.
• Figure 5: RCS measurement scenarios. (a) Experiment setups in the microwave anechoic chamber. (b) Transceiver equipment and targets.